One relatively new class of engines seeks to utilize two different fuels to gain the efficiencies associated with compression ignition combined with the advantages associated with burning natural gas fuel. In particular, one type of dual fuel engine utilizes a small pilot injection quantity of liquid diesel fuel that is compression ignited to in turn ignite a much larger charge of natural gas fuel in each engine cylinder. In one strategy for this type of engine, both fuels are directly injected from a single fuel injector associated with each engine cylinder. For instance, U.S. Pat. No. 7,627,416 appears to teach a dual fuel common rail system in which liquid diesel fuel and natural gas fuel are both injected from a single fuel injector associated with each engine cylinder. This reference recognizes that there may be instances in which the engine will need to operate solely on liquid diesel fuel due to exhaustion of the natural gas fuel supply or possibly some fault in the natural gas portion of the system. However, this reference fails to recognize the problems and challenges associated with transitioning from operating the dual fuel common rail system in a diesel only fueling mode back to a regular dual fuel mode.
The present disclosure is directed toward one or more of the problems set forth above.